The present invention relates to electronic data authenticity assurance techniques.
Electronic signature (also called digital signature) techniques have heretofore been known as techniques which perform authenticity assurance of electronic data such as electronic documents. (Refer to, for example, Bruce Schneier, Applied Cryptography: Protocols, Algorithms, and Source Code in C, Second Edition, John Wiley & Sons, (Oct. 18, 1995), pp. 483-502 (hereinafter referred to as Non-Patent Document 1)).
There are also techniques which take out individual entities of a structured electronic document as accessible and editable structured documents. (Refer to, for example, Japanese Patent Laid-open Publication No. 2001-167086 (FIG. 17) (hereinafter referred to as Patent Document 1)).
There are also techniques which are capable of deleting a portion permitted by a signer different from an owner from a document owned by the owner to which a signature is previously affixed by the signer, and which are capable of verifying the validity of the signed document after deletion. (Refer to, for example, Ron Steinfeld, Laurence Bull, Yuliang Zheng, Content Extraction Signatures, In International Conference on Information Security and Cryptology ICISC 2001, volume 2288 of LNCS, pp. 285-304, Berlin, 2001, Springer-Verlag, (2001) (hereinafter referred to as Non-Patent Document 2)).